The present invention relates to a method of transferring data between host computers employing a storage subsystem.
In recent years, xe2x80x9cthe down sizingxe2x80x9d for carrying out the operations of a business, conventionally carried out in a main frame, are now being performed by a small computer such as a personal computer or a workstation. A large amount of information generated as a result of operating the business is stored in the main frame and hence there is now a need for information stored on the main frame to be accessed by a small computer too. In addition, there is also the request that by using a high speed and highly reliable backup device connected to the main frame, backup for the data of the small computer is also desired.
Conventionally, with respect to the method of transmitting data between the different operating systems, there are well known an FTP (File Transport Protocol) and a distributed database.
In the above-mentioned prior art, a host computer of interest reads out temporarily data from a storage device such as a disk storage device and the data is delivered between the host computer through a network which has a protocol common to a plurality of host computers. But, the transfer rate of the network is relatively low and hence it is difficult to obtain a sufficient transfer rate. In addition, increase in the load on the network is not preferable in terms of the system.
In the light of the foregoing, the present invention was made in order to solve the above-mentioned problems associated with the prior art, and it is therefore an object of the present invention to provide a method of transferring data through a storage device such as a disk storage device instead of the network which has been conventionally used in the data transfer between the systems.
A computer system according to the present invention includes: a first computer; a second computer; a network for communication between the first and second computers; and a storage subsystem having a plurality of interfaces which are connected to the first and second computers.
The first and second computers are mutually accessible to data in the storage subsystem. When transferring the data from the first computer to the second computer, the first computer writes the transfer data to the storage subsystem. At the same time, the first computer writes to the storage subsystem the control information, which is required to transfer the data, such as the location in the storage subsystem to which the transfer data has been written. Then, the second computer reads out the control information which the first computer has written to the storage subsystem, and also on the basis of the control information thus read out, reads out the transfer data which the first computer has written to the storage subsystem.
After having read out the transfer data, the second computer writes to the storage subsystem the control information such as the location of the transfer data which the second computer has read out from the storage subsystem. Then, the first computer reads out the control information which the second computer has written to the storage subsystem, and recognizes that the second computer has completed the operation of reading out the transfer data, and also writes both of the transfer data and the control information to the storage subsystem again. In this connection, the transfer data can be overwritten to the region of the storage subsystem as long as the second computer has already read out the data from the region of interest. By repeating this processing, the data transfer from the first computer to the second computer can be realized. In addition, when writing the transfer data to the storage subsystem in this data transfer operation by the first computer, the data can be overwritten to the region of the storage subsystem as long as the second computer has already read out the data from the region of interest. For this reason, by utilizing repeatedly the same region of the storage subsystem, even in the case where the amount of transfer data is larger than the scale of the storage regions in the storage subsystem, the data transfer can be carried out. In addition, by replacing the roles of the first and second computers with each other, the data transfer from the second computer to the first computer is realized.
In addition, the above-mentioned data transfer can also be realized by carrying out only the delivery of the control information between the first and second computers through the network.